Since Jon knew that the stone was twisting wishes, you'd think that he would have been a bit more careful with his wishes, but no, he wasn't.
Karyn looked at Jon in shock. Or rather, she looked down at Jon in shock. Instead of Jon's uniform changing to match his age, his age changed to match his uniform. Now Jon was an elementary school student, which made him at least six years younger. He wasn't even a teen anymore!
"What have I done?" Jon said, in his higher-pitched boy's voice.